Instrument lighting arrangement



Feb. 15, 1955 A o-r 2,702,340

INSTRUMENT LIGHTING ARRANGEMENT Filed June 19, 1951 III. 70

Armand J. Thieblof INVENTOR.

\ HIS PATENT ATTORNEY.

much as possible the United States Patent 2,702,340 INSTRUMENT LIGHTING ARRANGEMENT Armand J. Thieblot, Hagerstown, Md.,-assignor to Fairchild Engine and Airplane Corporation, a corporation of Maryland Application June 19, 1951, Serial No. 232,364

3 Claims. (Cl. 2402.1)

The present invention relates generally to the lighting of instrument dials and the like and more particularly to improvements in centrally illuminated instrument dials.

To illuminate a dial and its indicia efficiently, uniformly and without causing the light rays to reach the eyes of the observer it is desirable that the light, source be centrally disposed and directed toward the center of the dial or illuminated area. The central location of the electric light source, however, presents the problem of carrying the wires across the glass or dial to the lamp and the wires present an undesirable obstruction to ones vision. Other efforts to provide improved illumination have mcluded positioning of the light source at the periphery or rim of the dial and resorting to various methods of diffusion for the distribution of the light over the entire dial area but such arrangements have in many respects proven unsatisfactory for'reasons of their complexity, expense in manufacture, and in certain cases failure to provide uniform glare-free illumination of the entire dial.

The present invention is directed to thelocation 0f the electric light source in the center of the glass cover, axially disposed with respect to the shaft of the instrument, where the shaft maybe centrally located, and energizing the lamp by means of electrically conductive transparent coatings on the cover glass. Such coatings are available today, principally as heating panels for the de-icing of windows, Windshields and the like. In instrument glass covers of normal size the resistance to the flow of current in such conductive coatings is relatively negligible and the glass is quite transparent and offers little obstruction to good visibility.

It is accordingly amajor object of the present invention to provide a dial lighting arrangement which will illuminate a dial efficiently, uniformly and without causing the light rays to reach the eyes of the observer with the exception of such unobjectionable light as is diffused and indirectly reflected from the indicia on the dial. A further object resides in the provision of a centrally lighted instrument dial in which the lamp is disposed in an area of the dial in which it does not interfere with the reading of the indicia on the dial, and in .an arrangement which obviates the necessity of carrying wires or other conductors across the cover glass in a condition in which they might interfere with the proper reading of the pointer on the dial. A further object resides in the provision of a relatively small source of light disposed on the back of the glass cover for supplying a substantially uniform distribution of lightradially outwardly from the lamp bulb toward the periphery of the dial and the cover.

It is a still further object to provide a light reflecting ring at the periphery of the dial preferably in the transverse plane containing the incandescent bulb for refleeting the light upon the indicia at the peripheral area of the dial. It is a further object of the invention to provide a transparent glass cover for an instrument which cover is at the same time a conductor of electric current for an illuminating lamp supported in a central lamp socket upon the glass cover and to thereby eliminate as glare reflected from the lamp into the eyes of the observer. It is also an object to provide an improved lamp socket or receptacle and arrangement for conducting electric current to the lamp. Further objects reside in the novel general arrangement of the present invention and in the details and cooperative relationship of the several elements which comprise the improved dial lighting arrangement.

Other objects and advantages of the present invention glass cover; and

Fig. 1 is a front elevational view of an instrument embodying a preferred form of the improved dial lighting arrangement;

Fig. 2 is an enlarged cross-sectional elevational view of the front portion of the instrument shown in Fig. l as taken along the lines 2-2;

Fig. 3 is an enlarged cross-sectional view of the lamp and its mounting in the central portion of the cover as indicated at 3 in Fig. 2;

Fig. 4 is a perspective view of the periphery of the Fig. 5 is a the cover.

Referring now to Figs. 1 and 2, the numeral 9 represents an instrument panel upon which the case of an instrument 10 is mounted as by the screws 11 extending through the holes 11a. The instrument is provided with a dial face 12 upon the periphery of which indicia may be provided as indicated in Fig. l, and the dial 12 may preferably be seated against the internal shoulder 13 of the instrument case 10. A shaft 14 extends centrally from the instrument through an axial opening in the dial 12 and carries upon its terminal the pointer or indicator 15. An annular reflector ring 16 having an inclined reperspective view of the central opening in fleeting surface 17 is preferably of such diameter that it fits within the cylindrical opening within the casing 10 and rests upon the periphery of the dial 12 which bears upon the shoulder 13 of the case. The reflector ring 16 has a cylindrical outer surface, tapers inwardly internally toward the dial 12 and its outer greater face dimension serves as a base for the glass cover 18. The glass cover 18 is provided on both of its faces with an electrically conducting coating of a transparent nature such as is presently available from a number of the larger glass manufacturers in this country. Such coatings are transparent, durable, and electrically conductive at a relatively low electrical resistance.

Panels of such electrically conductive glass have been successfully utilized as Windshields, such as proposed in Patent No. 2,429,420 which issued October 21, 1947, in which an electrical current passing through the conductive surface of the glass provides sufficient heat to defrost and de-ice the windshield panel. The glass may be in the form of a single thickness sheet as shown diagrammatically in the drawings for purposes of clarity, or it may be made up of laminations in which the electrically conductive surface may be laminated to one of the intermediate surfaces of a glass lamination which may preferably be an intermediate bonding layer of vinyl plastic. The electrically conductive coating is fired on the glass surface and in some of the types of glass which are presently available the surface produces an iridescent appearance by reflected light because of the selective reflections of the different wave lengths of light, but this color variation of reflected light is minimized by intermediately laminating the conductive surface. In an instrument glass cover of the type and size illustrated using a single plate of glass conductively coated on both faces the decrease in transparency is perhaps only 3 percent and has proven entirely satisfactory and serviceable.

The glass cover 18 is preferably of such diameter that it fits snugly within the circular opening within the easing 10, within which it is retained by the snap ring 19. A circular opening 18a is provided in the center of the glass cover 18 to receive the incandenscent lamp unit 21, to which the electric current is supplied by the outer conductive coating 20 and the inner coating 20a. The current to the incandescent lamp 21 is preferably supplied through the plug fitting 22 to which the wires 23 and 25 are connected, these wires terminating at their opposite terminals in the ring contact elements 24 and 26, respectively. These ring contacts provide electrical contact to the outer and inner conductive coatings 20 and 200 by means of the angular conductor contacts 40 and 41 which may preferably be of copper and embrace the bus bars 38 and 39, respectively, on the outer and inner faces of the glass cover 18.

The details of the lamp mounting are shown in Fig. 3

in which the lamp unit 21 comprises essentially an outer flanged cap element 28 which is preferably of metal and a conductor, and is provided within its tubular opening with an insert 29 of some suitable non-conducting mate rial such as fibre molded within the opening. An inner flanged fitting 30 of metal construction has a pair of locking cars 31 for engagement with the opening 310 pro vided in the fibre insert 29. A grain of wheat" lamp bulb 27 is retained within the inner metal fitting 30 which is in turn held within the opening 31a of the fibre insert 29 by the locking ears 31 and the fibre insert has a smaller coaxially disposed opening which receives the springpressed contact pin unit 32 urged outwardly by the com pression spring 33. An elastic cup-shaped washer 34 urges the fittings 28 and 30 apart 'for locking and unlocking purposes, this fitting bearing inwardly against the glass cover 18 at its outer periphery and outwardly against the peripheral flange on the outer fitting 28 by the inner portion of the washer 34. A bus bar 35 preferably of silver is fired on the outer surface of the glass cover 18 around the central opening 18a and a similar bus bar 36 is fired around the same opening at the inner surface of the glass cover 18. A-plurality of copper conductors 37 and 37a soldered to the bus bar 35 conducts current from the coating 20 on the outer face of the glass 18 to the fitting 28 and thence through the spring-pressed contact 32-33 to the positive electrode of the bulb unit 27. The direct contact of the inner fitting 30 with the inner bus bar 36 conducts current to the negative encasement of the bulb 27.

In order to conduct the current from the embedded wires 23 and 25, the above mentioned bus bar 38 is fired around the periphery of the outer surface of the glass cover 18 and the similar bus bar 39 is fired around the edge on the inside surface of the ,glass cover. A copper conductor 40 is soldered to the outer bus bar 38 and a similar conductor 41 is soldered to the inner bus bar 39 and makes contacts with the ring conductors 24 and 26 respectively to complete the electrical circuit. The bulb 27 is preferably coated at its tip portion as at 42 with paint or similar material in order that the bulb transmits light radially of its axis, or parallel to the dial face and inner face of the cover glass, for reflection of the laterally emitted light by the refiecting surface 17 of the reflecting ring 16 onto the face of the dial 12.

The location of the lamp unit is not confined to the central disposition shown but may be positioned to suit the requirements of the particular installation which may have the shaft located at other than the center and the glass cover may be of other than the circular shape shown. In any case the current may flow from the periphery of the cover to the lamp unit .without obstructing the vision of the user.

Other forms and modifications of the present invention which may occur to those skilled in the art after reading the foregoing description are intended to come within the scope and spirit of this invention as more particularly set forth in the appended claims.

I claim:

1. The combination with a transparent panel having electrically conductive coatings adhered thereto, and having an opening therein, of a lamp mounting carried by said panel within the opening, a lamp carried by said mounting receiving electrical energy through said conductive coatings, bus bars of curvilinear form constituting low resistance collector units being electrically connected to the opposite edges of each of said coatings, including the outer edges more remote from the opening and the inner edges immediately adjacent the opening, to extend throughout substantially the full length of said 4 I edges, the said bus bars being equidistantly spaced one from the other throughout their lengths to maintain uniformityof length of current flow path between all corresponding points throughout the lengths of the bus bars, and electrical connections extending from the collector units ad acent the opening to the said lamp mounting whereby upon connection of the remaining collector units to a source of electrical energy, current can flow through one coating to the lamp and from thence return through the other coating to the source.

2. In an instrument illuminating system, a transparent cover glass of circular mape having a central opening therein, an electrically energized source of illumination mounted in the opening, supply and return leads for conducting electricity for energizing said source, the said leads including transparent electrically conductive coatings applied to the surface of said cover glass to conform to the ring-shape of the glass, bus bars of curvilinear form constituting low resistance collector units applied to the edges of the respective transparent coatings adjacent the opening therein, the said bus bars being electrically connected to the coatings and to the source of illumination, and means for connecting each coating to one of the terminals of an electrical power supply so that a continuous circuit is formed leading from said power supply through the source of illumination and from thence back to the power supply, the current flow at any instant passing radially inward from the outer periphery of one ring shaped coating and radially outward from the inner periphery of the other ring-shaped coating, the said means including bus bars of curvilinear form constituting low resistance collector units electrically connected to the outer edges of the coatings.

3. In a mounting for an electric lamp, the combination of a mounting plate formed of transparent material, surface coatings adhered to opposite surfaces of said plate, the said coatings being selected from that class of materials which are both light transparent and electrically conductive, a lamp receptacle supported in a mounting aperture in said plate, the said receptacle including a pair of main body elements of conductive material adapted to project into the mounting aperture from opposite sides of the plate, means projecting from each body element adapted to react with respective opposite surfaces of the plate to limit penetration of each body element into the aperture, means making electrical connection between each body element and respective surface coatings, a supplementary body element of non-conductive material affixed to one of the main body elements, means forming a part of the other main body element having releaseable interengagement with the supplementary body element whereby the main body elements are locked together without electrical interconnection but are retained in the mounting aperture in electrical connection with the coatings, a socket formed in the body elements adapted to receive an electrical lamp, the socket formation supporting the lamp and including means providing electrical connections from the main body elements to the respective contacts of the lamp whereby energizing current may be fed through one coating, thence through a main body element to the lamp and from thence through the other main body element to the second coating.

References Cited in the file of this patent UNITED STATES PATENTS Re. 19,519 Douglas Apr. 9, 1935 2,172,765 Kollsman Sept. 12, 1939 2,429,420 MeMaster Oct. 21, 1947 2,599,710 Hathaway June 10, 1952 

